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TL and OSL properties of KAlSi(3)O(8):Mn, obtained by sol-gel process

PIRES, Elcio Liberato; TATUMI, Sonia Hatsue; MITTANI, Juan Carlos Ramirez; CALDAS, Linda V. E.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.06%
Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of KAlSi(3)O(8):Mn glasses obtained through the sol gel technique were investigated. Samples were obtained with five different molar concentrations of 0.25, 0.5, 1, 2 and 5 mol% of manganese. Transmission Electronic Microscopy (TEM) indicated the occurrence of nanoparticles composed by glass matrix elements with Mn. Best results for TL response were obtained with 0.5 mol% Mn doped sample, which exhibits a TL peak at 180 degrees C. The TL spectrum of this sample presents a broad emission band from 450 to 700 nm with a peak at 575 nm approximately. The emission band fits very well with the characteristic lines of the Mn(2+) emission features. According to this fact, the band at 410 nm can be ascribed to (6)A(1)(S) -> (4)A(1)(G), (4)E(G) transition, while the 545 nm band can be attributed to the superposition of the transitions (6)A(1)(S) -> (4)T(2)(G) and (6)A(1)(S) -> (4)T(1)(G). The dependence of the TL response with the energy of X-rays (27-41 keV) showed a small decrease of the TL intensity in the high energy region. Excitation with blue LEDs showed OSL in the UV region with a fast decay component. (C) 2011 Elsevier Ltd. All rights reserved.

Thermoluminescence properties of natural zoisite mineral under gamma-irradiations and high temperature annealing

Ccallata, Henry Sixto Javier; Tomaz Filho, Luiz; Watanabe, Shigueo
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.03%
Natural silicate mineral of zoisite, Ca(2)Al(3)(SiO(4))(Si(2)O(7))O(OH), has been investigated concerning gamma-radiation, UV-radiation and high temperature annealing effects on thermoluminescence (TL). X-ray diffraction (XRD) measurement confirmed zoisite structure and X-ray fluorescence (XRF) analysis revealed besides Si, Al and Ca that are the main crystal components, other oxides of Fe, Mg, Cr, Na, K, Sr, Ti, Ba and Mn which are present in more than 0.05 wt%. The TL glow curve of natural sample contains (130-150), (340-370) and (435-475)degrees C peaks. Their shapes indicated a possibility that they are result of composition of two or more peaks strongly superposed, a fact confirmed by deconvolution method. Once pre-annealed at 600 degrees C for 1 h, the shape of the glow curves change and the zoisite acquires high sensitivity. Several peaks between 100 and 400 degrees C appear superposed, and the high temperature peak around 435 degrees C cannot be seen. The ultraviolet radiation, on the other hand, produces one TL peak around 130 degrees C and the second one around 200 degrees C and no more. (C) 2010 Elsevier B.V. All rights reserved.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); CAPES; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP

Mechanisms of TL for production of the 230 degrees C peak in natural sodalite

Mamani, Nilo Francisco Cano; Blak, Ana Regina; AYALA-ARENAS, Jorge S.; Watanabe, Shigueo
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.18%
The thermoluminescence (TL) peak in natural sodalite near 230 degrees C which appears only after submitted to thermal treatments and to gamma irradiation has been studied in parallel with electron paramagnetic resonance (EPR) spectrum appearing under the same procedure This study revealed a full correlation between the 230 degrees C TL peak and the eleven hyperfine lines from EPR spectrum In both case the centers disappear at the same temperature and are restored after gamma irradiation A complete model for the 230 C TL peak is presented and discussed In addition to the correlation and TL model specific characteristics of the TL peaks are described (C) 2010 Elsevier B V All rights reserved; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[2007/08008-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

TL, OSL and ESR studies on beryllium oxide

Watanabe, Shigueo; Rao, Tumkur Krishnaswamy Gundu; PAGE, P. S.; BHATT, B. C.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
57.03%
Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermoluminescence (TL) and optically stimulated luminescence (OSL) processes in BeO phosphor. Two defect centres were identified in irradiated BeO phosphor by ESR measurements, which were carried out at room temperature and these were assigned to an O(-) ion and Al(2+) centre. The O(-) ion (hole centre) correlates with the main 190 degrees C TL peak. The Al(2+) centre (electron centre), which acts as a recombination centre, also correlates to the 190 degrees C TL peak. A third centre, observed during thermal annealing studies, is assigned to an O(-) ion and is related to the high temperature TL at 317 degrees C. This centre also appears to be responsible for the observed OSL process in BeO phosphor. (c) 2010 Elsevier B.V. All rights reserved.; CSIR; India Council for Scientific and Industrial Research (CSIR); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP, Brazil

Electron paramagnetic resonance and the thermoluminescence emission mechanism of the 280 degrees C peak in natural andalusite crystal

Mamani, Nilo Francisco Cano; Blak, Ana Regina; Watanabe, Shigueo
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47%
Samples of natural andalusite (Al(2)SiO(5)) crystal have been investigated in terms of thermoluminescence (TL) and electron paramagnetic resonance (EPR) measurements. The TL glow curves of samples previously annealed at 600 degrees C for 30 min and subsequently gamma-irradiated gave rise to four glow peaks at 150, 210, 280 and 350 degrees C. The EPR spectra of natural samples heat-treated at 600 degrees C for 30 min show signals at g = 5.94 and 2.014 that do not change after gamma irradiation and thermal treatments. However, it was observed that the appearance of a paramagnetic center at g=1.882 for the samples annealed at 600 degrees C for 30 min followed gamma irradiation. This line was attributed to Ti(3+) centers. The EPR signals observed at g=5.94 and 2.014 are due to Fe(3+). Correlations between EPR and TL results of these crystals show that the EPR line at g=1.882 and the TL peak at 280 degrees C can be attributed to the same defect center. (C) 2011 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[2007/08008-0]

Correlation between electron paramagnetic resonance and thermoluminescence in natural sodalite

Mamani, Nilo Francisco Cano; Blak, Ana Regina; Watanabe, Shigueo
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.14%
Samples of natural sodalite, Na(8)Al(6)Si(6)O(24)Cl(2), submitted to gamma irradiation and to thermal treatments, have been investigated using the thermoluminescence (TL) and electron paramagnetic resonance (EPR) techniques. Both, natural and heat-treated samples at 500A degrees C in air for 30 min, present an EPR signal around g = 2.01132 attributed to oxygen hole centers. The EPR spectra of irradiated samples show an intense line at g = 2.0008 superimposed by a hyperfine multiplet of 11 lines due to an O(-) ion in an intermediate position with respect to two adjacent Al nuclei. In the TL measurements, the samples were annealed at 500A degrees C for 30 min and then irradiated with gamma doses varying from 0.001 to 20 kGy. All the samples have shown TL peaks at 110, 230, 270, 365, and 445A degrees C. A correlation between the EPR g = 2.01132 line and the 365A degrees C TL peak was observed. A TL model is proposed in which a Na(+) ion acts as a charge compensator when an Al(3+) ion replaces a Si(4+) lattice ion. The gamma ray destruction of the Al-Na complex provides an electron trapped at the Na and a hole trapped at a non-bridging oxygen ion adjacent to the Al(3+) ion.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP[2007/08008-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Defect centre responsible for production of 110 degrees C TL peak in quartz

Farias, Thiago Michel de Brito; Watanabe, Shigueo; RAO, T. K. Gundu
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47%
110 degrees C thermoluminescence (TL) peak in quartz is well known due to its pre-dose effect, which is used in dating technique. The generally accepted mechanism for the production of this peak is based on Ge impurity contained in quartz. Its role is to substitute for Si in SiO(4) tetrahedron and under irradiation gives rise to [GeO(4)/e(-)](-) electron centre. Heating for TL read out liberates electron that recombines with hole in [AlO(4)/h]degrees or [H(3)O(4)/h]degrees centres emitting photon. The investigation, carried out on blue quartz, green quartz, black quartz, pink quartz, red quartz, sulphurous quartz, milky quartz, alpha quartz and synthetic quartz, has shown that the 110 degrees C TL peak in all these varieties of quartz has no correlation with the respective Ge content. Electron paramagnetic resonance (EPR) measurements on any of these varieties of quartz revealed a signal with g(1) = 2.0004, g(2) = 1.9986 and g(3) = 1.974 and this signal does not appear to correspond to any known EPR signals in alpha quartz. Furthermore, isothermal decay measurements are carried out on the above mentioned EPR signal and 110 degrees C TL peak in alpha, blue and green quartz. A close correlation has been observed in the decay behavior. A new mechanism is proposed based on an interstitial O(-) centre. (C) 2009 Elsevier Ltd. All rights reserved.; FAPESP; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dating archeological ceramics from the Valley of Vitor, Arequipa by the TL method

Mamani, Nilo Francisco Cano; ARIZACA, E. C.; YAURI, J. M.; ARENAS, J. S. A.; Watanabe, Shigueo
Fonte: TAYLOR & FRANCIS LTD Publicador: TAYLOR & FRANCIS LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.95%
The age of some ancient pottery from the Valley of Vitor in the region of Arequipa, Peru, is determined by the thermoluminescence (TL) method. For dating, a 325 degrees C TL peak was used and irradiation with -dose from 5 to 50Gy was carried out for the additive method, and from 0.4 to 5Gy for the regeneration method. For these dose values, the TL intensity is observed to grow linearly, obtaining an accumulated dose of 1.62 +/- 0.09Gy and 1.36 +/- 0.03Gy for the additive and regeneration methods, respectively. The age (A) of the sample was calculated by the two methods, being A=867 +/- 195 years after Christ (AC) for the additive method and A=1050 +/- 157 years AC for the regeneration method. Both results are within 800-1200 years AC, which is the period of the Wari culture.; FAPESP; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermoluminescence, structural and magnetic properties of a Li(2)O-B(2)O(3)-Al(2)O(3) glass system doped with LiF and TiO(2)

AYTA, W. E. F.; SILVA, V. A.; CANO, N. F.; SILVA, Marcelo de Assumpção Pereira da; DANTAS, N. O.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.03%
A Li(2)O-B(2)O(3)-Al(2)O(3) glass system, un-doped and doped with LiF, and/or TiO(2) was synthesized by the fusion method and its physical properties were investigated by thermoluminescence (TL), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), atomic force microscopy (AFM) and differential thermal analysis (DTA). The samples were subjected to gamma-rays from a colbalt-60 ((60)Co) source. These techniques provided evidence of LiF and LiF doped with Ti crystal formation in the glass system. A TL glow peak at about 433 K was sensitive to (60)Co gamma-rays and showed good linearity with doses and consequently could be used to quantify radiation doses. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.; Brazilian agency: CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG); Brazilian agency: FAPEMIG; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Brazilian agency: CAPES

Correlation between thermoluminescence sensitivity and crystallization temperatures of quartz: Potential application in geothermometry

Sawakuchi, André Oliveira; DEWITT, R.; FALEIROS, F. M.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.25%
The thermoluminescence (TL) characteristics of quartz are highly dependent of its thermal history. Based on the enhancement of quartz luminescence occurred after heating, some authors proposed to use quartz TL to recover thermal events that affected quartz crystals. However, little is know about the influence of the temperature of quartz crystallization on its TL characteristics. In the present study, we evaluate the TL sensitivity and dose response curves of hydrothermal and metamorphic quartz with crystallization temperatures from 209 +/- 15 to 633 +/- 27 degrees C determined through fluid inclusion and mineral chemistry analysis. The studied crystals present a cooling thermal history, which allow the acquiring of their natural TL without influence of heating after crystallization. The TL curves of the studied samples present two main components formed by different peaks overlapped around 110 C and 200-400 degrees C. The TL sensitivity in the 200-400 degrees C region increases linearly with the temperature of quartz crystallization. No relationship was observed between temperatures of quartz crystallization and saturation doses (<100 Gy). The elevated TL sensitivity of the high temperature quartz is attributed to the control exerted by the temperature of crystallization on the substitution of Si(4+) by ions such as Al(3+) and Ti(4+)...

Thermoluminescence and synchrotron radiation studies on the persistent luminescence of BaAl(2)O(4)/Eu(2+),Dy(3+)

RODRIGUES, L. C. V.; STEFANI, R.; BRITO, H. F.; FELINTO, M. C. F. C.; HOLSA, J.; LASTUSAARI, M.; LAAMANEN, T.; MALKAMAKI, M.
Fonte: ACADEMIC PRESS INC ELSEVIER SCIENCE Publicador: ACADEMIC PRESS INC ELSEVIER SCIENCE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.92%
The persistent luminescence materials, barium aluminates doped with Eu(2+) and Dy(3+) (BaAl(2)O(4): Eu(2+),Dy(3+)), were prepared with the combustion synthesis at temperatures between 400 and 600 degrees C as well as with the solid state reaction at 1500 degrees C. The concentrations of Eu(2+)/Dy(3+) (in mol% of the Ba amount) ranged from 0.1/0.1 to 1.0/3.0. The electronic and defect energy level structures were studied with thermoluminescence (TL) and synchrotron radiation (SR) spectroscopies: UV-VUV excitation and emission, as well as with X-ray absorption near-edge structure (XANES) methods. Theoretical calculations using the density functional theory (DFT) were carried out in order to compare with the experimental data. (C) 2010 Elsevier Inc. All rights reserved.; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Rede de Nanotecnologia Molecular e de Interfaces (RENAMI); Rede de Nanotecnologia Molecular e de Interfaces (RENAMI); IM2C (Instituto do Milenio de Materiais Complexos); Instituto do Milenio de Materiais Complexos (IM2C); Instituto Nacional de Ciencia e Tecnologia-Nanotecnologia para Marcadores Integrados (inct-INAMI); Instituto Nacional de Ciencia e Tecnologia-Nanotecnologia para Marcadores Integrados (inct-INAMI); Coimbra Group; Coimbra Group; Turku University Foundation; Turku University Foundation; Jenny and Antti Wihuri Foundation (Finland); Jenny and Antti Wihuri Foundation (Finland); Academy of Finland[112816/2006/JH]; Academy of Finland; Academy of Finland; Academy of Finland[116142/2006/JH]; Academy of Finland[123976/2007/TL]; Academy of Finland; European Community; European Community[RII3-CT-2004-506008 (IA-SFS)]; AVCR Academy of Sciences of the Czech Republic; AVCR Academy of Sciences of the Czech Republic

Propriedades de termoluminescência, de ressonância paramagnética eletrônica e de centros de cor de diopsídio; Thermoluminescence, electron paramagnetic resonance and color centers properties of diopside

Mamani, Nilo Francisco Cano
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/10/2007 PT
Relevância na Pesquisa
47.34%
No presente trabalho foram estudadas algumas propriedades de Termoluminescência (TL), Ressonância Paramagnética Eletrônica (RPE) e Refletância de uma amostra natural e de amostras artificiais de diopsídio. A curva de emissão TL das amostras tratadas termicamente a 600 `GRAUS´ C/1hr e irradiadas com dose gama mostraram um pico em aproximadamente em 160 `GRAUS´ C, que depois ficou demonstrado ser uma superposição de três picos em 160 `GRAUS´ C, 197 `GRAUS´ C e 230 `GRAUS´ C, além dos picos TL em 300 `GRAUS´ C, 350 `GRAUS´ C e 450 /C, mas de intensidade bem menor que os dos outros. Foram produzidas amostras artificiais de diopsídio, pelo método de devitrificação, uma pura e outras dopadas, separadamente, com Al, Fe e Mn. A amostra artificial pura apresentou todos os picos entre 160 e 350 `GRAUS´ C, encontrados no diopsídio natural, indicando que todos esses picos são devido a defeitos intrínsecos. A presença de Al e Mn afeta esses picos TL. O Fe, conhecido como "killer" abafa praticamente todos os picos, exceto o de 450 `GRAUS´ C que não depende de irradiação como os outros. O espectro de emissão TL da amostra natural apresentou uma banda em 435 nm indicando que só há um centro de recombinação, que é devido à presença de Al. A sensibilidade TL aumenta com o tratamento térmico antes da irradiação. Os picos TL crescem linearmente com a dose gama de irradiação...

Desenvolvimento e estudo de materiais termoluminescentes baseados em óxido de alumínio para aplicação em dosimetria; Development and study of thermoluminescent materials based on aluminum oxide for dosimetry application

Fukumori, David Tadashi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/04/2012 PT
Relevância na Pesquisa
47.15%
O óxido de alumínio foi um dos primeiros compostos investigados, com vista a detectar e medir a radiação por meio da termoluminescência (TL). Comumente referido como "alumina", o óxido de alumínio tem características interessantes para o desenvolvimento de materiais para a dosimetria. Seu número atômico efetivo é intermediário entre o do osso e do tecido mole do corpo. Pode ser transformado em material termoluminescente pela inserção de elementos químicos em sua estrutura cristalina. Além da TL, a alumina pode apresentar luminescência opticamente estimulada (OSL), fenômeno que também pode ser usado para determinar a dose de radiação. Neste estudo, dois métodos foram investigados para inserir íons metálicos na alumina. O primeiro método foi baseado na capacidade de adsorção da alumina e o segundo denominado método da coprecipitação foi baseado na formação simultânea de compostos insolúveis. As amostras obtidas por adsorção de íons Cu2+ e Mn2+ não mostraram resultados satisfatórios. No entanto, as pastilhas de óxido de alumínio impurificado com Tm3+ via coprecipitação mostraram sinais de TL e OSL. Foi verificado também que a alumina eletrofundida disponível comercialmente é um material que apresenta resposta TL e OSL. Este material que contém diversos íons metálicos em sua estrutura foi transformado em pastilhas por sinterização com vidro. As curvas da resposta TL em função da temperatura e da resposta TL e OSL em função da dose foram determinadas. Os resultados obtidos indicam que estudos mais aprofundados das pastilhas desenvolvidas podem melhorar suas características para que sejam aplicadas em dosimetria.; The aluminum oxide was one of the former compounds investigated with a view to detecting and measuring radiation by means of the thermoluminescence (TL). Commonly referred to as "alumina"...

Propriedades de absorção ótica (AO), de ressonância paramagnética eletrônica (EPR) e de termoluminescência (TL) do GROSSULAR - Cálculo do campo cristalino.; Properties of optical absorption (OA), of electron paramagnetic resonance (EPR), and of thermoluminescence (TL) of grossular-Calculation of the crystal field.

Yauri, Jessica Mosqueira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/11/2005 PT
Relevância na Pesquisa
47.14%
Granada é um grupo de seis silicatos com a mesma estrutura cristalina e fórmulas químicas semelhantes, diferindo um do outro pelos cátions, dos quais o GROSSULAR de fórmula química Ca IND.3Al IND.2Si IND.30 IND.12 é o segundo mineral mais abundante no Brasil, e talvez o mais colorido das granadas. Foram obtidas duas amostras de Araçuaí - Minas Gerais, denominadas GV e GVI que diferem somente no teor de impurezas, as quais foram pulverizadas e peneiradas para realizar medidas de Termoluminescência (TL) e Ressonância Paramagnética Eletrônica (EPR); e cortadas em lâminas e polidas para as medidas de Absorção Ótica(AO). A análise de fluorescência mostrou a presença de 1,37mol% de Fe IND.20 IND.3 na amostra GV e, 6,2mol% na GVI, 1,03mol% de MnO na GV e 0,26mol% na GVI, 0,66mol% de MgO na GV e 0,72mol% na GVI, que participam como defeitos extrínsecos na amostra. A curva de emissão termoluminescente apresentou um pico intenso em alta temperatura em 470ºC para as amostras naturais. Amostras tratadas termicamente em 600ºC/1h. e irradiadas com diferentes doses gama mostraram picos em 145, 235 e 335ºC em GV e em 145, 200, 250, 335 e 445ºC em GVI, mostrando-se mediante a deconvolução da curva TL que GV está formada de seis picos e GVI de sete picos bastante superpostos. Enquanto que em GV os picos de baixa temperatura crescem mais rápido com a irradiação...

Modelo de Armadilhas e Centros de Recombinação Interativos de Termoluminescência Face a Condições Teóricas e Dados Experimentais; Model of traps and interactive recombination centers of thermoluminescence compared to experimental data and theoretical conditions.

Ayta, Walter Elias Feria
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/08/2000 PT
Relevância na Pesquisa
47.41%
Neste trabalho faz-se uma analise teórica das curvas de emissão termoluminescente (TL) e das intensidades TL em função da dose da radiação, utilizando o chamado modelo de Sistema de Multi-armadilhas Interativas (SMAI). Esse modelo considera a participação de várias armadilhas (de elétrons para visualizar, mas, que pode ser, de buracos), entre as quais aquelas termicamente ativas (ATA), que dão origem ao pico TL com máximo em temperatura Tm; as armadilhas rasas (ARA), cujos picos TL ocorrem em T

Blue thermoluminescence emission of annealed lithium rich aluminosilicates

Correcher,V.; Rodriguez- Lazcano,Y.; Garcia- Guinea,J.; Crespo- Feo,E.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
Relevância na Pesquisa
47.03%
The blue thermoluminescence (TL) emission of different thermally annealed (i) β-eucryptite (LiAlSiO4), (ii) virgilite-petalite (LiAlSi5O12) and (iii) virgilite-petalite-bikitaite (LiAlSi10O22) mixed crystals have been studied. The observed changes in the TL glow curves could be linked to simultaneous processes taking place in the lithium aluminosilicate lattice structure (phase transitions, consecutive breaking linking of bonds, alkali self-diffusion, redox reactions, etc). The stability of the TL signal after four months of storage performed at RT under red light, shows big differences between annealed (12 hours at 1200ºC) and non-annealed samples. The fading process in non-annealed samples can be fitted to a first-order decay mathematical expression; however preheated samples could not be reasonably fitted due to the highly dispersion detected. The changes observed in the X-ray diffractograms are in the intensity of the peaks that denote modifications in the degree of crystallinity and, in addition, there are some differences in the appeareance of new peaks that could suppose new phases (e.g. β-spodumene).

Effect of particle size in the TL response of natural quartz sensitized by high dose of gamma radiation and heat-treatments

Carvalho Jr,Álvaro Barbosa de; Guzzo,Pedro Luiz; Sullasi,Henry Lavalle; Khoury,Helen Jamil
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
Relevância na Pesquisa
47.03%
This work investigates the effect of particle size in the thermoluminescence (TL) response of a quartz crystal that was initially crushed and classified into ten size fractions between 38 μm and 5 mm. Aliquots of each size fraction were sensitized with a dose of 25 kGy of γ rays and heat-treatments at 400 °C. TL glow curves of sensitized and non-sensitized samples were recorded as a function of different test-doses of γ rays. For the non-sensitized samples, the TL peak near 325 °C increases with the decrease in particle size. In the case of sensitized samples, a strong TL peak near 300 °C increases with the increase in particle size up to mean grain size equal to 304 μm. Above 304 μm, an abrupt reduction in the TL intensity is noticed for the sensitized peak. These effects are discussed in relation to the specific surface area of quartz particles and the intensity of the electron paramagnetic resonance signal of the E'1 center induced by the sensitization process.

Espectros de emisión de radioluminiscencia y termoluminiscencia de una leucita de Monte Somma (Italia); Radioluminescence and thermoluminescence emission spectra of a leucite of Monte Somma (Italy)

Valle Fuentes, Francisco José; García-Guinea, Javier; Correcher, Virgilio
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 271182 bytes; application/pdf
SPA
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[ES] La leucita natural (KAlSi2O6), materia prima para la fabricación de cerámicas dentales, es un material potencialmente válido para su utilización con fines dosimétricos ya que su respuesta luminiscente (radioluminiscencia -RL- y termoluminiscencia -TL-) en la región espectral del visible (200-800nm) es similar a la de otros aluminosilicatos utilizados también con fines dosimétricos. A pesar de la complejidad de las curvas, los espectros de emisión de TL y RL obtenidos con una leucita del Monte Somma (Nápoles, Italia) se pueden ajustar a un número máximo de seis funciones gaussianas situadas a 300, 380, 430, 480, 550 y 680 nm con significado físico. Este ajuste indica que en ambos procesos las trampas electrónicas que intervienen tienen el mismo origen. El análisis químico realizado por Fluorescencia de Rayos X (FRX) de la leucita estudiada permite intentar vincular el contenido de impurezas presentes en la red cristalina del material con las bandas de emisión que se producen como consecuencia de las distorsiones estructurales que se generan en la red cristalográfica formada por los tetraedros de SiO4 y [AlO4].; [EN] Natural leucite (KAlSi2O6), one of the main components of dental ceramics, shows similar radioluminescence (RL) and thermoluminescence (TL) response than other aluminosilicates (in the 200-800nm region) employed for dosimetric purposes. Despite the complex structure of the emission spectra...

Caracterización de la curva de termoluminiscencia del circón a partir de su contenido radiactivo y del análisis térmico diferencial; Characterization of the thermoluminescence curve of zircon by radiactive content and differential thermal analysis

Correcher, Virgilio; Valle Fuentes, Francisco José; García-Guinea, Javier; Robredo, L. M.; López-Arce, Paula
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 217249 bytes; application/pdf
SPA
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[ES] El circón (ZrSiO4) es un material que se utiliza habitualmente en la fabricación de refractarios, esmaltes para azulejos, pigmentos, etc. Este mineral tiene un alto contenido radiactivo debido a la presencia de emisores alfa naturales como U y Th. En este trabajo se ha determinado el contenido isotópico de estos radionucleidos (238U, 235U y 234U, 228Th, 230Th y 232Th) utilizando técnicas de separación radioquímicas y cuantificando la actividad mediante espectrometría alfa. Estos radioisótopos naturales producen una irradiación interna en el material cerámico que se manifiesta en sus propiedades luminiscentes lo que implica que pueda ser utilizado con fines dosimétricos. Se ha observado que la curva de termoluminiscencia (TL) del circón muestra una intensidad considerablemente mayor (más de un orden de magnitud) que la de otros silicatos medidos en idénticas condiciones. Los máximos que aparecen en la curva de TL se correlacionan con distintos puntos de inflexión que aparecen en la medida de análisis térmico diferencial (ATD), a 280, 360 y 445oC, lo que indica que estos picos de TL aparecerán como consecuencia de: (1) procesos parciales de transiciones de fase locales y (2) fenómenos de autodifusión iónica y deshidroxilación que se producen durante el calentamiento al realizar la medida.; [EN] Zircon (ZrSiO4) is a mineral widely employed in the production of refractories...

Thermoluminescence characteristics of the irradiated minerals extracted from red pepper (Capsicum annuum L.) spice

Marcazzó,J.; Cruz-Zaragoza,E.; Montiel,L.; Chernov,V.; Calderón,T.
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
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The inorganic polymineral content in the foodstuffs allows to analyze the main thermoluminescence (TL) characteristics that may be useful in the identification of irradiated food. The mineral fraction was separated from commercial Mexican red pepper (Capsicum annuum L.). X-ray diffraction shows that the mineral composition of the samples was mainly quartz. From the mineral fraction of different grain sizes, samples of 149 μm were selected for this study because of the high TL signals. The samples were irradiated from 1 to 500 Gy by using a 60Co irradiator. The TL characteristics like glow curve shape, dose-response, UV and sunlight bleaching and fading were analyzed. The glow curves show an intense TL peak at 82 ºC followed by others with less intensity at 130, 170 and 340 ºC. The TM-TSTOP method shows six TL glow peaks that was taken into account for calculation the activation energies values. Because the complex structure of the glow curves, the kinetics parameters were determined by using a computerized deconvolution program assuming the general order kinetics model.